18Ni maraging steel disc and method of making

Abstract

The application belongs to the field of metallurgy and pressure processing, and discloses a 18Ni maraging steel round disc and a preparation method thereof. The preparation method comprises the following steps: carrying out primary smelting on a Ni plate, metal cobalt, a molybdenum strip, sponge Ti and industrial pure iron in a vacuum induction furnace to obtain a molten steel; pouring the molten steel into a consumable electrode, and carrying out secondary remelting on the consumable electrode in a vacuum consumable furnace to obtain a steel ingot; carrying out blooming on the steel ingot to obtain a billet; rolling the billet into a bar; and carrying out heat treatment and discing on the bar to obtain the 18Ni maraging steel round disc. The length of the 18Ni maraging steel bar is increased from 2-12 meters to more than 2000 meters through the rolling method, and the problem of large end material waste caused by the short length and large number of 18Ni maraging steel bars is solved.

Description

Technical Field

[0001] This invention belongs to the field of metallurgy and pressure processing, and particularly relates to an 18Ni martensitic aging steel wire rod and its preparation method. Background Technology

[0002] 18Ni martensitic aging steel is a high-alloy steel with ultra-high strength, composed of Fe-Ni matrix with added alloying elements such as Co, Mo, Ti, and Al. Its alloy ratio exceeds 30%. After solution treatment and aging heat treatment, it has ultra-high strength and good toughness, as well as good welding and cold working properties. It is widely used in aviation, aerospace and high-end civilian products.

[0003] Currently, the main types of 18Ni martensitic aging steel produced domestically include forged bars, forgings, rolled bars, and plates. Small-diameter bars (φ5-φ10) are typically manufactured using hot rolling. According to GB / T702 "Dimensions, Shape, Weight and Permissible Deviations of Hot-Rolled Steel Bars," the bar length should be 2-12 meters. However, in subsequent deep processing, the bar ends cannot be machined or are unusable due to their short length, resulting in significant waste. Increasing the bar length to over 20 meters would cause major transportation inconvenience and would not fundamentally solve the problem of excessive waste due to unfinished end sections.

[0004] Therefore, it is necessary to provide a 18Ni martensitic aging steel wire rod and its preparation method, which changes the material shape of 18Ni martensitic aging steel from rolled bar to rolled wire rod, greatly increasing the bar length, reducing the waste of end bar material, and making transportation very convenient. Summary of the Invention

[0005] In order to overcome the defects of the existing technology, the purpose of this invention is to provide a 18Ni martensitic aging steel wire rod and its preparation method. By changing the material shape of the 18Ni martensitic aging steel from rolled bar to rolled wire rod, the length of the bar is greatly increased, the waste of end bar material is reduced, and transportation is very convenient.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing 18Ni martensitic aging steel discs, characterized by comprising:

[0008] Ni plate, metallic cobalt, molybdenum strip, sponge Ti and industrial pure iron are smelted in a vacuum induction furnace to obtain molten steel.

[0009] Molten steel is cast into consumable electrodes and then remelted in a vacuum consumable furnace to obtain steel ingots.

[0010] The steel ingot is cut into billets to obtain billets;

[0011] Roll the billet into bars;

[0012] The bar stock was heat-treated and coiled to obtain 18Ni martensitic aging steel coils.

[0013] Furthermore, a secondary remelting is performed in a vacuum arc remelting furnace, including:

[0014] Control the melting rate at 3-6 kg / min.

[0015] Further, the steel ingot is roughened, including:

[0016] Heat the steel ingot to above 1200℃ and hold it at that temperature for at least 20 hours;

[0017] The heated steel ingots are processed into 140-200 cubic meter pieces using a press or rolling mill. 5.7-6.1 meter billet.

[0018] Further, the billet is rolled into bars, including:

[0019] Heat the billet to 1110-1170℃ and hold for at least 30 minutes;

[0020] The heated billet is rolled at an initial rolling temperature of ≥1050℃ and a final rolling temperature of ≥950℃.

[0021] Further, the bar stock undergoes heat treatment and coiling, including:

[0022] Heat the bar to 820-860℃ and hold at that temperature for at least 6 hours;

[0023] The heated bar is then coiled into a round shape.

[0024] Furthermore, the mass percentages of each component in the steel ingot include: C≤0.02wt%, Mn≤0.10wt%, Si≤0.10wt%, S≤0.010wt%, P≤0.010wt%, 17.00wt%≤Ni≤19.00wt%, 7.00wt%≤Co≤13.00wt%, 3.50wt%≤Mo≤5.50wt%, 0.40wt%≤Ti≤1.60wt%, with the balance being iron and impurities.

[0025] Furthermore, the mass percentages of each component in the steel ingot include: 0.0045 wt% C, 0.02 wt% Mn, 0.02 wt% Si, 0.003 wt% S, 0.003 wt% P, 18.15 wt% Ni, 12.08 wt% Co, 4.55 wt% Mo, 1.45 wt% Ti, with the balance being iron and impurities.

[0026] Secondly, the present invention discloses an 18Ni martensitic aging steel disc, which is prepared by the above-described method.

[0027] Furthermore, when the diameter of the 18Ni martensitic aging steel coil is φ8.5mm, the tensile strength at room temperature is ≥2408MPa, the yield strength is ≥2288MPa, the elongation is ≥9.5%, the reduction of area is ≥53%, and the hardness is ≥55HRC.

[0028] Furthermore, the mass percentages of each component in the 18Ni martensitic aging steel wire rod include 0.0045 wt% C, 0.02 wt% Mn, 0.02 wt% Si, 0.003 wt% S, 0.003 wt% P, 18.15 wt% Ni, 12.08 wt% Co, 4.55 wt% Mo, 1.45 wt% Ti, with the balance being iron and impurities.

[0029] The technical effects and advantages of this invention are as follows:

[0030] This invention increases the length of 18Ni martensitic aging steel bars from the usual 2-12 meters to over 2000 meters by using a rolling coil method, thus solving the problem of significant waste of end material caused by the short length and large number of 18Ni martensitic aging steel bars.

[0031] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0032] Figure 1 This is a flowchart of a method for preparing 18Ni martensitic aging steel discs according to the present invention. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] like Figure 1 As shown, this invention provides a method for preparing 18Ni martensitic aging steel discs, comprising:

[0035] Ni plate, metallic cobalt, molybdenum strip, sponge Ti and industrial pure iron are smelted in a vacuum induction furnace to obtain molten steel. After the metal is melted into molten steel, the composition is homogenized by stirring and H, O and N gaseous elements in the molten steel are removed.

[0036] Molten steel is cast into consumable electrodes and then remelted in a vacuum consumable furnace to control the residual elements such as S, P, and C in the steel to a relatively low range, thus obtaining steel ingots.

[0037] The steel ingot is cut into billets to obtain billets;

[0038] Roll the billet into bars;

[0039] The bar stock was heat-treated and coiled to obtain 18Ni martensitic aging steel coils.

[0040] In some embodiments of the present invention, secondary remelting is performed in a vacuum arc remelting furnace, including:

[0041] Control the melting rate at 3-6 kg / min.

[0042] In some embodiments of the present invention, the steel ingot is roughened, including:

[0043] The steel ingot is heated to above 1200℃ and held at that temperature for at least 20 hours to homogenize the chemical composition of the steel ingot;

[0044] The heated steel ingots are processed into 140-200 cubic meter pieces using a press or rolling mill. The billet is 5.7-6.1 meters long. The surface of the billet is then polished to remove iron oxide scale and small cracks. After the end is flattened, it is inspected for flaws according to the Class B requirements of GB4162 standard.

[0045] In some embodiments of the present invention, rolling the billet into a bar includes:

[0046] Heat the billet to 1110-1170℃ and hold it for at least 30 minutes. If the temperature is too high, it will cause coarse grains and affect the material properties. If the temperature is too low, due to the long rolling mill track, the temperature drop will be large, which will easily lead to a sharp increase in deformation resistance during rolling and rolling accidents. The optimal holding temperature is 1150℃.

[0047] The heated billet is rolled at an initial rolling temperature of ≥1050℃ and a final rolling temperature of ≥950℃.

[0048] In some embodiments of the present invention, heat treatment and coiling of the bar stock include:

[0049] The bar is heated to 820-860℃ and held at that temperature for at least 6 hours to soften it. The optimal holding time is 8 hours.

[0050] The heated bar is then coiled into a round shape.

[0051] In some embodiments of the present invention, the mass percentages of each component in the steel ingot include: C≤0.02wt%, Mn≤0.10wt%, Si≤0.10wt%, S≤0.010wt%, P≤0.010wt%, 17.00wt%≤Ni≤19.00wt%, 7.00wt%≤Co≤13.00wt%, 3.50wt%≤Mo≤5.50wt%, 0.40wt%≤Ti≤1.60wt%, with the balance being iron and impurities.

[0052] In some embodiments of the present invention, the mass percentages of the components in the steel ingot include: 0.0045 wt% C, 0.02 wt% Mn, 0.02 wt% Si, 0.003 wt% S, 0.003 wt% P, 18.15 wt% Ni, 12.08 wt% Co, 4.55 wt% Mo, 1.45 wt% Ti, with the balance being iron and impurities.

[0053] On the other hand, the present invention discloses an 18Ni martensitic aging steel disc, which is prepared by the above method.

[0054] In some embodiments of the present invention, when the diameter of the 18Ni martensitic aging steel coil is φ8.5mm, the tensile strength at room temperature is ≥2408MPa, the yield strength is ≥2288MPa, the elongation is ≥9.5%, the reduction of area is ≥53%, and the hardness is ≥55HRC.

[0055] In some embodiments of the present invention, the mass percentages of each component in the 18Ni martensitic aging steel wire rod include 0.0045 wt% C, 0.02 wt% Mn, 0.02 wt% Si, 0.003 wt% S, 0.003 wt% P, 18.15 wt% Ni, 12.08 wt% Co, 4.55 wt% Mo, 1.45 wt% Ti, with the balance being iron and impurities.

[0056] To better illustrate this solution, the following embodiments are also provided.

[0057] Example 1

[0058] S1: Ni plate, metallic cobalt, molybdenum strip, sponge Ti and industrial pure iron are smelted in a vacuum induction furnace to obtain molten steel. After the metal is melted into molten steel, the composition is uniformly stirred and H, O and N gaseous elements in the molten steel are removed.

[0059] Molten steel is cast into consumable electrodes and then remelted in a vacuum consumable furnace at a melting rate of 3-6 kg / min. The residual elements such as S, P, and C in the steel are kept within a relatively low range to obtain steel ingots. The chemical composition of the steel ingots is 0.0045 wt% C, 0.02 wt% Mn, 0.02 wt% Si, 0.003 wt% S, 0.003 wt% P, 18.15 wt% Ni, 12.08 wt% Co, 4.55 wt% Mo, 1.45 wt% Ti, with the balance being iron and impurities.

[0060] S2: Heat the steel ingot to above 1200℃ and hold for at least 20 hours to homogenize the chemical composition of the ingot. Then, use a press to cut the heated steel ingot into billets to obtain 140 cubic meters. The 5.7-meter billet is then polished to remove iron oxide scale and small cracks. After the ends are flattened, it is inspected for defects according to the Class B requirements of GB4162 standard.

[0061] S3: Heat the billet to 1110℃ and hold it for at least 30 minutes. Roll the heated billet with an initial rolling temperature ≥1050℃ and a final rolling temperature ≥950℃ to obtain a bar.

[0062] S4: Heat the bar to 820℃ and hold for 6 hours. Then, coil the heated bar to obtain φ8.5mm 18Ni martensitic aging steel coils.

[0063] Example 2

[0064] S1: Ni plate, metallic cobalt, molybdenum strip, sponge Ti and industrial pure iron are smelted in a vacuum induction furnace to obtain molten steel. After the metal is melted into molten steel, the composition is uniformly stirred and H, O and N gaseous elements in the molten steel are removed.

[0065] Molten steel is cast into consumable electrodes and then remelted in a vacuum consumable furnace at a melting rate of 3-6 kg / min. The residual elements such as S, P, and C in the steel are kept within a relatively low range to obtain steel ingots. The chemical composition of the steel ingots is 0.0045 wt% C, 0.02 wt% Mn, 0.02 wt% Si, 0.003 wt% S, 0.003 wt% P, 18.15 wt% Ni, 12.08 wt% Co, 4.55 wt% Mo, 1.45 wt% Ti, with the balance being iron and impurities.

[0066] S2: Heat the steel ingot to above 1200℃ and hold for at least 20 hours to homogenize the chemical composition of the ingot. Then, use a press to cut the heated steel ingot into billets, obtaining 200 cubic meters. The 6.1-meter billet is then polished to remove iron oxide scale and small cracks. After the ends are flattened, it is inspected for defects according to the Class B requirements of GB4162 standard.

[0067] S3: Heat the billet to 1170℃ and hold it for at least 30 minutes. Roll the heated billet with an initial rolling temperature ≥1050℃ and a final rolling temperature ≥950℃ to obtain a bar.

[0068] S4: Heat the bar to 860℃ and hold for 8 hours. Then, coil the heated bar to obtain φ8.5mm 18Ni martensitic aging steel coils.

[0069] The mechanical properties and length of the 18Ni martensitic aging steel discs prepared in Examples 1 and 2 were tested at room temperature. The results of the mechanical property tests are shown in Table 1.

[0070] Table 1 Mechanical properties of 18Ni martensitic aging steel wire rods

[0071]

[0072] As shown in Table 1, the 18Ni maraging steel wire rods prepared by the method of the present invention, with a diameter of φ8.5mm, exhibit a tensile strength ≥2408MPa, a yield strength ≥2288MPa, an elongation ≥9.5%, a reduction of area ≥53%, and a hardness ≥55HRC at room temperature, meeting the standard requirements. The 18Ni maraging steel wire rods prepared in Examples 1 and 2 are both over 3400 meters in length, significantly longer than the conventional 2-12 meter length of 18Ni maraging steel bars. This greatly increases the length, solving the problem of significant waste of end material due to short lengths and numerous bars in 18Ni maraging steel, and also greatly facilitates transportation.

[0073] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing 18Ni martensitic aging steel wire rods, characterized in that, include: Ni plate, metallic cobalt, molybdenum strip, sponge Ti and industrial pure iron are smelted in a vacuum induction furnace to obtain molten steel. The molten steel is cast into a consumable electrode and then remelted in a vacuum consumable furnace to obtain a steel ingot. The steel ingot is cut into billets to obtain billets; The billet is rolled into a bar; The bar stock is heat-treated and coiled to obtain 18Ni martensitic aging steel coils. The aforementioned secondary remelting in a vacuum arc remelting furnace includes: Control the melting rate at 3-6 kg / min; The process of roughing the steel ingot includes: The steel ingot is heated to above 1200°C and held at that temperature for at least 20 hours. The process of rolling the billet into bars includes: The billet is heated to 1110-1170°C and held at that temperature for at least 30 minutes. The heated billet is rolled at an initial rolling temperature of ≥1050℃ and a final rolling temperature of ≥950℃. The heat treatment and coiling of the bar stock includes: The bar is heated to 820-860℃ and held at that temperature for at least 6 hours. The heated rod is then coiled into a round shape. The steel ingot contains the following components by mass percentage: 0.0045 wt% C, 0.02 wt% Mn, 0.02 wt% Si, 0.003 wt% S, 0.003 wt% P, 18.15 wt% Ni, 12.08 wt% Co, 4.55 wt% Mo, 1.45 wt% Ti, with the balance being iron and impurities.

2. The method for preparing 18Ni martensitic aging steel discs according to claim 1, characterized in that, The process of roughing the steel ingot includes: The heated steel ingots are processed into billets of 140-200 cubic meters × 5.7-6.1 meters by press or rolling.

3. A type of 18Ni martensitic aging steel wire rod, characterized in that, It is prepared by the method described in any one of claims 1-2.

4. The 18Ni martensitic aging steel wire rod according to claim 3, characterized in that, When the diameter of the 18Ni martensitic aging steel coil is φ8.5mm, the tensile strength at room temperature is ≥2408MPa, the yield strength is ≥2288MPa, the elongation is ≥9.5%, the reduction of area is ≥53%, and the hardness is ≥55HRC.

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